1. Field of the Invention
This invention relates to a catheter assembly for sensing internal fluid pressure and aspirating fluids from a wound and, more particularly, to a needle for inserting the catheter assembly in the body tissue.
2. Description of Related Art
Following surgical procedures in or around the human heart, it is often desirable to monitor the pressure of the fluid in or around the heart. More particularly, it is desirable to measure the pressure of the blood within the left atrium of the heart. The pressure is measured by inserting one end of a fluid-filled catheter into the superior pulmonary vein and attaching the other end of the fluid-filled catheter to a pressure sensing device. This is commonly known as a left atrial catheter. Monitoring the left atrium pressure with a left atrial catheter is one way of measuring the strength of the heart following surgery and in evaluating the proper time to remove a heart pump from a heart surgery patient. The sterility of the end of the catheter which is mounted in the superior pulmonary vein is paramount. The introduction of infection causing microorganisms into the heart can be deadly.
The left atrial catheter is typically mounted in the body cavity through an incision in the skin and body tissue or through an opening created by a catheter needle. The catheter assembly can be inserted "inside to outside", i.e. from the wound side to the external skin surface, or it can be inserted "outside to inside", i.e. from the skin surface through the body tissue to the wound side. Regardless of the method of introducing the catheter, it is imperative that all steps be taken to reduce to a minimum the chance of infection of the wound.
Examples of catheter needles which are mounted inside to outside are disclosed in U.S. Pat. No. 4,976,684 to Broadnax, Jr. and U.S. Pat. No. 4,792,328 to Beck et al. Each of these catheter assemblies includes a needle or trocar which is first used to create an opening in the skin and body tissue and then to guide the catheter from the wound side of the body tissue to the external skin surface.
The more traditional procedure for inserting the catheter is outside to inside. However, this procedure has one significant drawback. Even when the skin has been assiduously prepared, introducing the needle from the external skin surface can result in the introduction of microorganisms from the skin into the wound via the needle. Unfortunately, known catheter assemblies are not adapted to prevent or reduce exposure of the catheter to the potentially contaminated external skin surface. Examples of known catheter assemblies which do not address this problem are disclosed in U.S. Pat. No. 3,861,393 to Durand, U.S. Pat. No. 4,496,353 to Overland et al., U.S. Pat. No. 4,490,136 to Ekbladh et al., U.S. Pat. No. 4,617,019 to Fecht et al. and U.S. Pat. No. 4,883,474 to Sheridan et al.
Another known method of introducing the catheter is to use a catheter having an internal stylet. The catheter and internal stylet are passed through the skin and body tissue outside to inside. Unfortunately, this procedure can result in damage to the catheter when passing through the skin. For example, the tip of the catheter can slide back on the internal stylet similar to an accordion, thereby damaging the fragile catheter tip. Secondly, microorganisms present on the skin surface can become lodged inside the catheter tip and the bevel of the stylet. This procedure is not acceptable.
Catheters are also mounted in a body cavity to remove fluids within the body cavity. Body tissue that has been subject to a wound or an internal surgical procedure often secretes fluid. It is necessary to remove fluid thus secreted within a body cavity in order to promote healing and prevent infection of the wound. Catheters have long been used to aspirate secreted fluid from a wound in a body cavity. These catheters are often mounted inside to outside and outside to inside as discussed above.